The invention relates to flexible pipes and tubular conduits, but more particularly, the invention relates to flexible hose which includes distinct layers and spirally wound material.
Pressure hose is typically reinforced to overcome longitudinal extension and radial expansion with twined strands, which may be of a textile material, steel wire, or the like; or the reinforcement may be of a sheet-like material such as square woven fabric or cord type fabric. In either case, the reinforcement is applied to provide desired radial and longitudinal strength to a pressurized hose. The lay of the reinforcement is typically chosen to have a minimum affect on hose twisting, or changes in radial and longitudinal dimensions when the hose is pressurized.
Special purpose pressure hoses such as buoyant hose include the typical reinforcements to maintain longitudinal and radial hose dimensions. Additional structure is included to obtain necessary buoyancy. For example, floats may be attached to the hose such as disclosed in U.S. Pat. No. 3,489,182. Other hose designs include integral float chambers filled with a foamed material. An example of such a hose is disclosed in U.S. Pat. No. 3,194,274.
Another type of buoyant hose with integral foam chambers is disclosed in U.S. Pat. No. 3,119,415. In the '415 patent, a single piece of tubing filled with foam is spiralled around a reinforced hose at a helical angle near 90.degree. in a layer of foam. Such a single ply reinforcement gives radial strength to the hose at radial points of contact therewith but offers very little, if any, longitudinal strength and resistance to twisting in a direction oposite the spiral of the reinforcement.
Such prior art pressure hose constructions have two major disadvantages. First, such pressure hoses are heavier than necessary because the hose is reinforced to withstand pressure using conventional reinforcement techniques. Float systems whether they be built within or attached to the hose, must be sufficiently voluminous and of low specific gravity to off-set the specific gravity of added hose reinforcements to achieve buoyancy.
Second, those hose constructions with unsupported integral foam, allow the foam to be compressed or water logged which negates buoyancy. These hoses typically have an excessive reserve buoyancy to counteract the problem. A reserve buoyancy is demanded by users for the purpose of obtaining extended hose service life.
A type of hose where tubing is used as a float and solely as a radial reinforcement is disclosed in U.S. Pat. No. 3,117,596 and British Pat. No. 1,361,215. One or more pieces of tubing are spiralled laterally adjacent at substantially identical helical angles to form one ply of tubing. Carcass reinforcement plies are necessary to provide longitudinal and twist resistant strength for a pressure type hose. The single ply of tubing acts solely as a radially reinforcement. It cannot act as a twist and longitudinal tension resistant reinforcement.